Tumblr is now a rarity for displaying GIFs at all. Most popular sites—including Twitter and Imgur—convert GIF uploads and serve the animations as MP4 videos. As Kohler explained to me, video compression has improved so much over the years that many video files are much smaller than GIF image files. He pulled a GIF from a movie and a graphic-art GIF to show me the difference. The GIF from the movie was nearly 4.5 megabytes, and the MP4 translation of it was about 20 times smaller, at less than .23 megabytes. “MP4 is the right choice for this kind of image,” he said. “Much smaller, very similar visual effect.”

https://www.theatlantic.com/technology/archive/2022/10/using-reaction-gifs-over-tumblr-giphy/671680/